In recent years, small and thin image pickup units have been mounted on portable electronic terminal devices such as mobile phones and PDAs (Personal Digital Assistants). Such image pickup units generally have a solid-state image pickup device such as a Charge Coupled Device (CCD) image sensor or a Complementary Metal-Oxide Semiconductor (CMOS) image sensor, and a lens for forming an image of the subject on the solid-state image pickup device.
With miniaturization and thickness reduction of portable terminals and propagation of portable terminals, further miniaturization and thickness reduction of image pickup units to be mounted thereon are requested, together with provision of adequate productivity. To cope with such a request, a mass-production method of an image pickup unit is known whereby a lens substrate having plural lenses formed thereon and a sensor substrate having plural solid-state image pickup devices formed thereon are integrally combined, and the lens substrate and the sensor substrate are cut in such a manner that each of the cut substrates includes a lenses and solid-state image pickup devices. Other production methods include, for example: a method of fabricating an image pickup unit whereby only lenses are formed on a glass wafer, the glass wafer is cut to have a size suitable for combined use with an individual sensor substrate piece, and combined with an individual image pickup substrate piece that has been cut to have an appropriate size in advance, and is then combined with an image pickup device which had been individualized in advance; a method whereby plural lenses are formed in a mold by using only a resin, the lenses are combined disposed on and combined with a sensor substrate, and cutting the resultant, and a method of fabricating an image pickup unit whereby a lens substrate is cut to have an size appropriate for combination with an individual sensor substrate piece, and is combined with an image pickup substrate piece that has been cut to have an appropriate size in advance.
Hereinafter, in the present specification, each of plural lenses formed on a lens substrate is referred to as “wafer level lens”, and a lens group formed on a lens substrate, inclusive of the lens substrate, is referred to as “wafer level lens array”.
A conventional wafer level lens array is known which is obtained by dripping a curable resin material on a surface of a flat plate substrate formed of a light-transmissive material such as glass, shaping the resin material into a given shape in a mold, and curing the resin material in this state to form plural lenses (for example, see Japanese Patent No. 3,926,380 and International Publication No. WO 2008/102648). In some cases, a light-shielding region made of a black film, a metal film, or the like is formed at a region other than the lens region of the wafer level lens, or at a portion of the lens, in order to control an amount of light. The light-shielding region is generally formed by applying a curable light-shielding composition or depositing a metal.
Another wafer level lens array is known which is obtained by forming plural holes through a silicon substrate, separately-prepared spherical lens material is disposed at each through hole, fusing the lens material to the substrate by soldering, and polishing the lens material to form plural lenses (see U.S. Pat. No. 6,426,829). The lens obtained by this method may be provided with a black film, a metal film, or the like similar to the above, in order to control an amount of light.
Formation of a light-shielding region by deposition of a metal has problems in that the process is complex, the lens bends after deposition, and light scattering occurs due to reflection by the metal light-shielding film, and further improvements are requested from the viewpoint of both productivity and performance.
In order to exert light-shielding properties, a carbon black-containing black curable composition for use in, for example, black matrices of LCDs is employed for the application. However, provision of sufficient light-shielding properties in the visible light region for use with a lens also causes insufficient light transmittance for a radiation selected from g-line, h-line, i-line, or the like as an exposure light source used for the curing of the curable composition, and, resultantly, inability of the curing to proceed to deep into the film, and peeling of the film during a development process after image-wise exposure.